Understanding Safety / General

Human Factors

Even though the human element is considered vital in the aviation operations and this importance is widely acknowledged, humans are not perfect and studies attribute more than two thirds (2/3) of accidents to human error. Even if not directly or as the last point of error, human is considered a contributing element to 70-80% of accidents. It is thus of paramount importance for safety experts to gain an understanding of human factors; that is the human decision-making process as well as the interactions around the people (see SHELL model). Human Factor studies aim to understand how the correct management of human beings can increase their efficiency and performance to yield an error-free judgement, especially at critical situations. It is important to note that not only pilot form the group of front line decision makers, but any front-line employee like air traffic controllers, engineers, operations personnel etc. ICAO list the following areas when describing Human Factors: aeronautical design, certification, training, operations and maintenance.

Poor decision making is what is considered the basic element of human factors that contributes to accidents. Three main reasons make up this decision-making model: incomplete information, inaccurate or irrelevant information, or poor information processing.

The limited information processing has been already explained by the field of psychology, where Miller’s Law states that the maximum number of irrelevant items an average human brain can process in its working memory is 7 (+/- 2). That is the main reason accidents tend to happen in situations of high workload (e.g. take-off & landing) or task saturated situations or in situations of physical exhaustion. The concept of CRM, sterile cockpit and SOPs helped in controlling the information processing of pilots.

Understanding human factors is a complicated science as the data can be soft, i.e. not consistent and not precise. Something we tend to accept when we state that each human is an individual person. Human factors science attempts to optimise the field of aviation environment by encompassing fields of psychology, anthropology, biomechanics etc along with engineering, information technology etc.

The main emphasis is given on the capabilities and limitations of individuals under specified conditions, in a complex systemic and multi-interactive environment. It is important to realise that when evaluating human performance, i.e. the level of accuracy in a performed task, the deliberate disregard or violation of rules and procedures is not considered.

We can classify the human factors in 7 categories. These categories can stand alone or they can be combined depending on the situation.

  1. Physical factors
  2. Physiological factors
  3. Psychological factors (in the following personality traits)
    • Motivation
    • Memory
    • Complacency
    • Attention
    • Attitude
    • Perceptions
    • Self-discipline
    • Risk taking
    • Judgment
  4. Psychosocial factors
    • Peer pressure
    • Ego related
  5. Hardware factors
  6. Task factors
  7. Environmental factors

In a very similar concept and using the same basis, for the scope of SMS data, ICAO has standardised these 7 categories as below:

  1. Environmental/ System Design (ENVR)
    • Operating Environment/Design
    • Physical Environment
    • Environmental Conditions
    • Task Environment/Design
  2. Experience/ Knowledge (KNOW)
    • Experience
    • Qualifications/Training
    • Knowledge
  3. Organisational Oversight (ORGN)
    • Oversight
    • Operational Planning/Scheduling/Resource Management
    • Policy/Procedures
    • Training Program
    • Documentation/Record Keeping
    • Enforcement
    • Safety Program
  4. Perceptual (PERC)
    • Situational Awareness
    • Spatial Disorientation/Illusions
  5. Physical/ Sensory (PHYS)
    • Physical Characteristics
    • Sensory Ability/Limitation
    • Impairment/Incapacitation
    • Health/Fitness
    • Fatigue/Alertness
  6. Procedural/ Task Performance (PROC)
    • Planning/Preparation
    • Documentation/Record Keeping Tasks
    • Information/Equipment Utilization
    • Monitoring
    • Workload Management
    • Communication
    • Coordination
    • Violations
    • Action/Inaction
  7. Psychological (PSYC)
    • Attention/Distraction
    • Cognitive Limitation
    • Information Processing/Decision Making
    • Mental/Emotional State
    • Personality/Attitude

Based on the Swiss Cheese Model, the Human Factors Analysis and Classification System (HFACS), provides the following diagram of barriers in human factors.

HFACS framework

Human error control and management can be helped with the use of the following strategies, concepts and tools:

  • CRM
  • LOSA
  • TEM
  • Cockpit Standardisation
    • Sterile Cockpit procedures
    • Communication

With today’s technology and reliability aircraft are rather managed than flown. The automation has not reduced the workload in the sense and perception of the public. It has reduced the workload during the phase of cruise, where it had already been low. It has however increased or complicated the workload during the take-off and approach and landing phases where it was already high. For this reason, we’ve seen many perfectly flying and airworthy aeroplanes being managed into disasters. It is argued that many modern flight decks today are rich in data presentation but poor in providing information.

The human factors integration model aims to provide a holistic framework taking in mind the elements of staffing, personnel, training, engineering, health and safety.

Human factors is like health. When everything works fine, no one notices, as everything goes right with minimum effort. But as soon as something breaks out everybody panics.

The individual differences is an issue in crew selection, as some traits are desirable for the job, but the connecting traits they bring along are not. This brings up the personality theory which proposes types of personality, classifying people into distinct and discrete categories. The four basic dimensions are:

Extroversion / Introversion: how the person’s energy is directed. Outwards towards people or inwards towards self
Sensing/ Intuitive: how is new information received, perceived and interpreted. Tangible and hard information- facts, or abstract concepts

Thinking/ Feeling: Decision making based on logic and rational toolset versus empathy and needs of people
Judging/ Perceiving: interaction process with external world. Structured approach to life or a flexible and adaptable lifestyle

Furthermore, we have a long list of stressors that could affect the attitude and behaviour of person, that is how the personality is expressed outwards. Stress is a product of the individual’s perceived demands exceeding the perceived abilities to cope with a task. For this reason, it varies dramatically with each person and is irrelevant of the actual individual’s abilities.

The stressors can be classified as environmental, work related, domestic related and life related. Aircraft design and engineering focuses on the environmental stressors. These include but not limited to, vibrations, noise level, light level, comfort, temperature, humidity, general air quality etc.

Stress is expressed physiological (sweating, heart rate), through health, through behaviour, cognitively or subjectively (through feelings). However, stress is not always unwanted. A normal level of stress can increase arousal which is desired, especially when dealing with a difficult task. Arousal can range from zero (coma) through unconsciousness, sleep, wakefulness, alert, to high performance. Over arousal is unhealthy (overstress) whilst too low arousal can lead to boredom.
Stress dealing is an individualistic issue and the techniques are subject to personal preferences. As a general guide though, the following are considered positive stress coping techniques:

  • Physical health through exercise and balanced diet
  • Personality through wellbeing and self-acceptance
  • Personal life through solid foundations
  • Bodily rest and ease of mind
  • General preparation for the required task

A common resort for stress coping, which is however very tricky and dangerous, is alcohol consumption. Even though in its initial stages alcohol relaxed the body, removes tensions and aids in sleeping, it promotes dehydration (which means irritability and increased pulse) which then escalates to headaches, dizziness etc. Sleep becomes ineffective and the body does not properly rests.